1. Field of the Invention
This invention relates to new, water soluble adjuvant compositions for use in spray carriers containing postemergence herbicides, which are used to control weeds or other undesired vegetation in crops.
2. Description of the Prior Art
Herbicides used in controlling weeds or undesired vegetation in agriculture are customarily applied by postemergence spraying of a herbicide on the crop. The spray carrier for the herbicide is usually a water based solution containing an effective amount of known herbicide.
Adjuvants are commonly added to herbicidal spray solutions to enhance postemergence weed control and/or to reduce spray drift during herbicide applications.
Postemergence weed control requires that the spray containing the herbicide be retained on the weed surface for that purpose. To obtain that result, many "sticker" compositions or agents, including methylated vegetable oils or mineral based oils and wetting (surface/active) agents are marketed for spray solution adherence of the herbicide by the weeds and in addition help retain droplets of the spray solution on the plant and to penetrate into the plant.
In addition to spray retention by the weed, other additives in the form of liquid nitrogen based fertilizer solution have been found, for example, to enhance the control of wild oats by herbicides such as Barban. Miller et al., Weed Science, 1978, Vol. 4, pp. 344-348. Recently surfactants have been combined with liquid fertilizers (usually 28% nitrogen and comprising a mixture of 50% ammonium nitrate and 50% urea). The results however are variable depending on surfactants used and nitrogen fertilizer employed. It was found that certain salts and surfactants influence nicosulfuron, for example, and its herbicide activity. Nalewaja et al., Weed Technology, 1995, Vol. 9, pp. 587-593.
Some acidic additives have previously been used which are designed to lower pH and enhance the acidity of the spray carrier water formulation which was believed to both benefit herbicide adsorption and also to prevent alkaline hydrolysis of certain insecticides. Acids and buffering agents are sometimes also used to reduce antagonism from alkaline salts found in the spray carrier water.
It has been noted that adjuvants differ greatly in herbicide enhancement depending on the specific surfactant and the herbicide used in some cases resulting in decreased performance. Halloway, 4th International Symposium on Adjuvants for Agrochemicals, 1995, FR. & Bulletin, No. 193).